How to forward GNUPG GPG Agent via SSH

I wanted to know how to use GPG keys securly in such a way like I already do with SSH keys: private key always kept on my local host while it is usable on remote hosts via SSH connection.

SSH client side

GPG Agent needs to be run. The agent is usually started on demand by gpg, gpgsm, gpgconf or gpg-connect-agent.

gpg-connect-agent /bye

The usual way to run the agent is from the ~/.xsession file:

eval $(gpg-agent --daemon)

For my convenience, I like to add hosts to .ssh/config file:

Host vm
  RemoteForward /run/user/1000/gnupg/S.gpg-agent

SSH server side

Change SSH daemon's config to allow recreating stale gpg unix sockets.

Edit /etc/ssh/sshd_config file:

StreamLocalBindUnlink yes

GPG agent should be stopped to release related unix socket.

ps aux | grep gpg
kill [pid]

Public key must be present

gpg --keyserver --search [EMAIL ADDRESS]

Now reconnect to the SSH sever and validate if all fine:

gpg -K
gpg -k